ebiten/audio/vorbis/vorbis.go

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// Copyright 2015 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package vorbis provides Ogg/Vorbis decoder.
package vorbis
import (
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"fmt"
"io"
"runtime"
"github.com/hajimehoshi/ebiten/audio"
"github.com/hajimehoshi/ebiten/audio/internal/convert"
)
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// Stream is a decoded audio stream.
type Stream struct {
decoded audio.ReadSeekCloser
size int64
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}
// Read is implementation of io.Reader's Read.
func (s *Stream) Read(p []byte) (int, error) {
return s.decoded.Read(p)
}
// Seek is implementation of io.Seeker's Seek.
//
// Note that Seek can take long since decoding is a relatively heavy task.
func (s *Stream) Seek(offset int64, whence int) (int64, error) {
return s.decoded.Seek(offset, whence)
}
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// Close is implementation of io.Closer's Close.
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func (s *Stream) Close() error {
runtime.SetFinalizer(s, nil)
if err := s.decoded.Close(); err != nil {
return err
}
return nil
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}
// Length returns the size of decoded stream in bytes.
func (s *Stream) Length() int64 {
return s.size
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}
// Size is deprecated as of version 1.6.0-alpha. Use Length instead.
func (s *Stream) Size() int64 {
return s.Length()
}
type decoder interface {
Read([]float32) (int, error)
SetPosition(int64) error
Length() int64
Channels() int
SampleRate() int
}
type decoded struct {
totalBytes int
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readBytes int
posInBytes int
source io.Closer
decoder decoder
decoderr io.Reader
}
func (d *decoded) Read(b []byte) (int, error) {
if d.decoderr == nil {
d.decoderr = convert.NewReaderFromFloat32Reader(d.decoder)
}
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l := d.totalBytes - d.posInBytes
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if l > len(b) {
l = len(b)
}
if l < 0 {
return 0, io.EOF
}
retry:
n, err := d.decoderr.Read(b[:l])
if err != nil && err != io.EOF {
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return 0, err
}
if n == 0 && l > 0 && err != io.EOF {
// When l is too small, decoder's Read might return 0 for a while. Let's retry.
goto retry
}
d.posInBytes += n
if d.posInBytes == d.totalBytes || err == io.EOF {
return n, io.EOF
}
return n, nil
}
func (d *decoded) Seek(offset int64, whence int) (int64, error) {
next := int64(0)
switch whence {
case io.SeekStart:
next = offset
case io.SeekCurrent:
next = int64(d.posInBytes) + offset
case io.SeekEnd:
next = int64(d.totalBytes) + offset
}
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// pos should be always even
next = next / 2 * 2
d.posInBytes = int(next)
d.decoder.SetPosition(next / int64(d.decoder.Channels()) / 2)
d.decoderr = nil
return next, nil
}
func (d *decoded) Close() error {
runtime.SetFinalizer(d, nil)
if err := d.source.Close(); err != nil {
return err
}
d.decoder = nil
d.decoderr = nil
return nil
}
func (d *decoded) Length() int64 {
return int64(d.totalBytes)
}
// decode accepts an ogg stream and returns a decorded stream.
func decode(in audio.ReadSeekCloser) (*decoded, int, int, error) {
r, err := newDecoder(in)
if err != nil {
return nil, 0, 0, err
}
d := &decoded{
// TODO: r.Length() returns 0 when the format is unknown.
// Should we check that?
totalBytes: int(r.Length()) * r.Channels() * 2, // 2 means 16bit per sample.
posInBytes: 0,
source: in,
decoder: r,
}
runtime.SetFinalizer(d, (*decoded).Close)
if _, err := d.Read(make([]byte, 65536)); err != nil && err != io.EOF {
return nil, 0, 0, err
}
if _, err := d.Seek(0, io.SeekStart); err != nil {
return nil, 0, 0, err
}
return d, r.Channels(), r.SampleRate(), nil
}
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// Decode decodes Ogg/Vorbis data to playable stream.
//
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// Decode returns error when decoding fails or IO error happens.
//
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// Decode automatically resamples the stream to fit with the audio context if necessary.
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func Decode(context *audio.Context, src audio.ReadSeekCloser) (*Stream, error) {
decoded, channelNum, sampleRate, err := decode(src)
if err != nil {
return nil, err
}
if channelNum != 1 && channelNum != 2 {
return nil, fmt.Errorf("vorbis: number of channels must be 1 or 2 but was %d", channelNum)
}
var s audio.ReadSeekCloser = decoded
size := decoded.Length()
if channelNum == 1 {
s = convert.NewStereo16(s, true, false)
size *= 2
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}
if sampleRate != context.SampleRate() {
r := convert.NewResampling(s, size, sampleRate, context.SampleRate())
s = r
size = r.Length()
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}
stream := &Stream{decoded: s, size: size}
runtime.SetFinalizer(stream, (*Stream).Close)
return stream, nil
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}